The sun doesn't ever heat the Earth evenly. Depending on the Earth's natural formations as well as its orientation to the sun, some spots get heated more than others. As some air gets heated, it becomes less dense, and thus lighter, and naturally floats upward. This leaves an open space for denser, colder air to rush in and take its place. This air rush is the refreshing cool breeze you feel on a sunny day.
Wind is also responsible for our very powerful waves. As wind rushes up along the water, the friction causes ripples. Wind continues to push against these ripples in a snowball effect that eventually creates a large wave. Essentially, this action is a transfer of energy from the sun to the wind to the waves.
A few factors determine how strong an individual wave will be. These include:
- Speed of wind: The faster the wind is traveling, the bigger a wave will be.
- Time of wind: The wave will get larger the longer the length of time the wind is hitting it.
- Distance of wind: The farther the wind travels against the wave (known as fetch), the bigger it will be.
Interestingly, waves move energy, not water, far distances. Water works as the medium through which kinetic energy, or energy in motion, passes. The water is moving, of course, but only in a circular motion. In other words, water particles work as rollers in a conveyor belt do -- they rotate in order to move the belt on top forward, but they themselves don't go forward in the process. This is why buoys will rise and fall in a vertical motion with the water.
But if we already have wind turbines to harness wind energy, why use ocean waves? Though they may seem like an unnecessary middleman, waves have a few advantages over wind when it comes to gleaning usable energy. For one thing, ocean waves are dense with energy. In other words, whereas wind might take up a lot of space to contain some energy, waves can collect a great amount of energy and pack it into a small space.
Another advantage is that ocean waves are reliable -- we can more easily predict which way the waves will be moving than which way the wind will be blowing. Also, wind can start a wave and then on its own, the wave can travel a great distance. Large waves that travel far from their origin are called swell waves. This means that the entire surface of an ocean can collect energy, and without us doing any work, the waves come to us, even from very far away.
Now that we know how waves gain their energy, let's take a look at how we can collect that energy.